This invention relates to traffic control systems of the radio controlled type, and more particularly to an improved digital system including a common transmitting unit which communicates with one or more receiving units by transmitting enabling digital characters thereto. The receiving units are respectively coupled to control associated traffic signalling units, each in control of the traffic flowing in a particular direction. The receiving units receive all of the transmitted digital characters, but are respectively programmed to actuate their associated traffic signalling units differently in response to different possible ones of the transmitted digital characters. The receiving units when thus enabled by digital characters actuate their own associated traffic control indication means to display selected indications to the traffic flowing in the direction which the signalling units control. The present digital control system lends itself well to portable traffic control requirements, but is not limited thereto since it can also control other devices, for instance, such as the movements of a crane.
In a typical temporary control situation, for instance at a construction or repair site, the flow of traffic is often limited to a single lane in which traffic flows alternately in opposite directions. In order to substantially reduce labor costs, it is desirable to be able to replace the two flagmen often used in a two-way situation with a single traffic-control system having one operator supervising the flow of traffic using a transmitting unit to actuate remote receiving and signalling units in the system located at the ends of the construction site, one signalling unit for each traffic flow direction, and each remote signalling unit being responsive to outputs from its own receiving unit which receives all of the digital characters radiated as signals from the transmitting unit. There are a number of patented systems using radio control of traffic signalling units.
For instance, U.S. Pat. Nos. 2,829,362 to Terrill Mullikin and 3,046,521 to Cantwell et al show portable traffic control systems used to control either crossed-intersection or alternate one-way single lane traffic, using wired as well as radio controlled techniques. U.S. Pat. Nos. 3,247,482 to Lesher and 3,159,817 to Hendricks et al show the use of radio controlling intersection traffic light systems, the former controlling installed lights by transmissions radiated from an emergency vehicle to ease its way through normal traffic, and the latter showing radio systems for normal control of traffic flow.
Several more recent traffic control patents include U.S. Pat. Nos. 3,867,718 to Moe and 4,401,969 to Green et al. However all of the above prior disclosures are either hard-wired or else radiate unmodulated RF control signals or radiate RF signals modulated with one or more audio tones which are then demodulated and separated by filtering at the receiving units to obtain control information by which their signals are actuated. The latter systems work well enough in isolation from other spurious interfering radiations, but in todays environment where there are so many radio signals radiated for communications and various radio control purposes, the reliability of tone controlled systems is not sufficient to insure proper immunity from accidental wrong responses. Although there exist digital control systems, for instance for garage doors as shown in U.S. Pat. Nos. 3,906,348 and 4,037,201 to Wilmott, no prior disclosure is known that meets all of the requirements for traffic control systems as will be discussed hereinafter.
In addition, here are government regulatory requirements imposed upon all traffic controllers, including portable units. Most of these requirements are imposed by the Manual on Uniform Traffic Control Devices (MUTCD), issued by the U.S. Department of Transportation, Federal Highway Administration. These regulations must be met at all construction and repair sites which are funded in whole or part by federal money. Since such a high proportion of sites involves federal funding, most of the states have adopted the MUTCD regulations as standard for their own, as well as federally funded projects. These regulations are very detailed, and therefore require a more sophisticated radio control system than has been used in the past. Moreover, in order to be sure of meeting these regulations, it is desirable to remove, from discressionary control by the operator handling the system, the full capability of controlling the precise sequence of events, as well as the dwell times of some of the traffic indications so that he can not perform the sequence incorrectly in violation of the MUTCD regulations. The present invention makes many of the function sequences and time durations automatic, and automatically limits many options formerly left to the operator, whereby the MUTCD requirements are always met and failsafe procedures are in all cases carried out to avoid dangerous or confusing indications to oncoming traffic.
The regulations specified by the MUTCD cover almost all phases of traffic control and safety. Among them are regulations including specific requirements that are of particular concern in the present disclosure, for instance specifying for traffic control lights their luminosity, their lens and reflector diffusion patterns, their structural characteristics, the roadway positions and numbers of lights controlling lanes of traffic, requirements for special functions such as flashing caution lights, minimum durations of traffic light displays, etc. These and other requirements will be discussed in more detail hereinafter at locations in this disclosure where the information is particularly pertinent.
In view of the specificity of the MUTCD regulations, it is more practical to buy and use standard traffic light assemblies having government approved physical construction, lenses, reflectors and bulbs, etc., than to alter the light assemblies and bulbs to make them easier to use in portable traffic control situations. When alterations are made, one is then faced with having to obtain approval from the federal government as well as all 50 states. There exists no screw-base D.C. bulb that will replace the approved A.C. bulbs in traffic controller use, while at the same time preserving the required luminosity and the filament position with respect to the reflectors and lenses. Accordingly when the present disclosure is used in the form of a portable unit it is necessary to provide a 110 volt A.C. power source to supply the lights themselves, thereby making a special configuration of portable power supply necessary.